Addiction-as-a-kind hypothesis

The psychiatric category of addiction has recently been broadened to include new behaviors. This has prompted critical discussion about the value of a concept that covers so many different substances and activities. Many of the debates surrounding the notion of addiction stem from different views concerning what kind of a thing addiction fundamentally is. In this essay, we put forward an account that conceptualizes different addictions as sharing a cluster of relevant properties (the syndrome) that is supported by a matrix of causal mechanisms. According to this “addiction-as-a-kind” hypothesis, several different kinds of substance and behavioral addictions can be thought of as instantiations of the same thing—addiction. We show how a clearly articulated account of addiction can facilitate empirical research and the theoretical integration of different perspectives on addiction. The causal matrix approach provides a promising alternative to existing accounts of the nature of psychiatric disorders, the traditional disease model, and its competitors. It is a positive addition to discussions about diagnostic criteria, and sheds light on how psychiatric classification may be integrated with research done in other scientific fields. We argue that it also provides a plausible approach to understanding comorbidity. In recent years, the concept of addiction, as it is used both in research and in policy contexts, has been expanded to include new behaviors (e.g., gambling, eating, sex, shopping, exercise, even internet use). There has also been critical discussion about the value of a concept that covers so many different substances and activities. In this essay, we present an account of the conditions under which several kinds of substance and behavioral addictions can be thought of as instantiations of the same thing—addiction. We call this account the “addiction-as-a-kind” hypothesis. The account describes what addiction would look like if it were a legitimate psychiatric kind. We call it a hypothesis because it is an empirical question whether different addictions really constitute such a kind. In this essay, we will not assess the empirical support for the hypothesis, but will focus on describing some of its general characteristics. In other words, we describe what a general theory of addiction could look like. The paper is structured as follows. First we frame our theory by briefly considering some difficulties with the traditional disease model and its alternatives. Then we present our addiction-as-a-kind hypothesis and the underlying causal matrix view of psychiatric kinds. The final section discusses the issue of comorbidity and, based on the hypothesis, offers some suggestions for addiction research. The Problem With the Traditional Disease Model There has been a longstanding debate in psychiatry concerning the nature of psychiatric disorders, with still no agreement on what psychiatric illnesses actually are. The traditional disease model that conceptualizes psychiatric illnesses based on a model drawn from medicine is still commonly accepted (Kincaid & Sullivan, 2010; cf. Leshner, 1997). This model builds on essentialist thinking, as it presumes that psychiatric illnesses can be understood as well-determined entities having a few causal core properties, which in turn explain the rest of their properties. Moreover, it is usually assumed that this essence must lie within the afflicted individual. One example of a medical condition satisfying the essentialist model is Huntington’s disease. The genetic basis of Huntington’s forms its causal core, in the sense that it can be used to explain many of the properties of the condition. Psychiatric disorders create difficult problems for the medical model. Most psychiatric disorders seem to have multiple contributing and sustaining causes (Murphy, 2010). Furthermore, in many cases there is a continuum of severity of the disorder, without a clear-cut established difference between the disorder and the normal state. Both considerations are problematic for an account that aims to identify the disease with a single well-defined etiological cause that is clearly separate from normal functioning. IJADR International Journal of Alcohol and Drug Research The Official Journal of the Kettil Bruun Society for Social and Epidemiological Research on Alcohol 22 Petri Ylikoski and Samuli Pöyhönen –––––– IJADR 4(1) –––––– Furthermore, the traditional medical model seems to be implicitly biased in favor of “biological” causes, thus making it difficult to integrate an understanding of the influence of psychological and social mechanisms with knowledge of neural and genetic processes (Kincaid & Sullivan, 2010). These problems suggest that the traditional disease model is not a good starting point for developing a general theory of addiction. However, no consensus exists on an alternative approach. Psychiatric classification systems such as DSM and ICD are purely descriptive, and while serving several administrative and clinical purposes, they are a poor foundation for a scientific study of the causes of psychiatric disorders (Adam, 2013; Craddock & Owen, 2010; Murphy, 2006). Likewise, we do not think that accounts that view addiction as normal choice-behavior under exceptional circumstances (Heyman, 2009) can really solve the problem, as they have trouble incorporating findings about the cognitive and neural processes underlying addictive behavior. In debates about addiction (and other mental disorders), the traditional disease model often serves as a straw man that is easy to criticize. Because a positive alternative to it is missing, the failure of the traditional disease model fuels skepticism about the whole notion of addiction. The purpose of our addiction-as-a-kind hypothesis is to provide a viable alternative to the traditional disease model of addiction. A clearly articulated account of addiction as a psychiatric kind may aid in facilitating discussions about the diagnostic criteria, definition, and classification of addiction, insofar as it may provide a context for developing substantive theories about the disorder. It would also conceptually facilitate the integration of neuroscientific, psychological, and social scientific insights into a substantive synthetic theory of addiction. It is apparent that many of these benefits do not depend on the addiction-as-a-kind hypothesis being true. A false theory can also be fruitful in directing research (see Wimsatt, 2007), whereas a complete lack of a theory rarely is. The Addiction-as-a-Kind Hypothesis Our replacement for the traditional model is based on the mechanistic property cluster view of kinds (Boyd, 1999), which has been developed in the philosophy of science over the last 30 years, and has more recently been applied to psychiatric kinds (Kendler, Zachar, & Craver, 2010; Kuorikoski & Pöyhönen, 2012; Murphy, 2006). We believe that this account provides a reasonable middle way between the medical model, the pragmatic kinds theory (Zachar, 2003), and more minimalist approaches that conceive of having a mental illness as nothing more than meeting diagnostic criteria. In our proposal, a psychiatric kind consists of two